1. Field of the Invention
The present invention relates to a control apparatus of a vehicle mounting an engine thereon.
2. Description of Related Art
In the case that a driver performs a rough starting operation (clutch operation or accelerator pedal operation) at a time of starting in a manual transmission loaded vehicle (hereinafter, refer to as an MT vehicle), there is a case that an extreme drop of an engine rotating speed or an engine stall is generated. This is because the engine rotating speed is lowered if a clutch torque (corresponding to a load torque in the case of viewing from the engine side) in accordance that a connection of the clutch is advanced, and a clutch torque begins to get over a shaft torque of the engine. Accordingly, in order to inhibit the engine rotating speed from being lowered at a time of connecting the clutch, it is necessary for the driver to further step on an accelerator pedal at a suitable timing and to adjust an engine torque in such a manner as to overcome the load torque.
This operation can be comparatively easily performed on the basis of a longtime accumulation of experience, for an expert driver, however, it is hard for an inexperienced driver to accurately execute this operation. Accordingly, it is desirable to carry out the engine torque operation mentioned above in a vehicle side for compensating a skill of the driver. However, in a conventional engine control system using a mechanical throttle, since a throttle valve corresponding to a main torque control device works with the accelerator pedal, a freedom of the engine torque control is low, and it is hard to execute the torque operation in the engine side at a time of starting.
On the other hand, in recent years, there comes into practical use an engine control system using an electronically controlled throttle in place of the conventional mechanical throttle. In this system, since a throttle opening degree can be set with respect to an accelerator opening degree, a control freedom of the engine torque is high. Accordingly, in the system using the electronically controlled throttle, there have been laid open several techniques for controlling the torque control of the engine in such a manner as to assist the starting operation of the driver.
For example, in patent document 1 (JP-A-2001-73840), there is described a technique for switching a relation between “accelerator opening degree and throttle opening degree” which is generally set linear to a nonlinear relation. The feature of this technique exists in setting the throttle opening degree to an open side in comparison with the normal time with respect to the accelerator opening degree, near the accelerator opening degree which is normally used for connecting the clutch, in the case of a vehicle speed range in which the starting operation is expected. In accordance with this setting, it is possible to adjust the engine torque for overcoming the load torque at the starting time without the driver deeply stepping the accelerator pedal, and it is possible to lighten the load of the driver.
In the technique described in the patent document 1, an increment of the throttle opening degree is calculated in accordance with a feedforward control having the accelerator opening degree as an input. However, the accelerator operation and the clutch operation of the driver are various at a time of starting the MT vehicle, and the accelerator opening degree range normally used at the starting time and the increasing range of the throttle opening degree do not necessarily coincide for some driver, so that there is a case that the torque assist effect can not be sufficiently obtained.
Further, in the range in which the throttle opening degree is set larger with respect to the accelerator opening degree, since a throttle opening degree change is sensitive with respect to the accelerator operation, there has been generated a problem that it is hard to adjust the engine rotating speed before connecting the clutch, or the engine rotating speed does not rise up linearly at a time of racing.